Non-volatile memory devices are widely used in many consumer, commercial and other applications. Non-volatile memory devices using a resistive material include, for example, a resistive random access memory (RRAM), a phase change RAM (PRAM), and a magnetic RAM (MRAM). While a dynamic RAM or a flash memory uses charge to store data, the non-volatile memory device using the resistive material stores data using a variation in the resistance of a variable resistive material (RRAM), a variation in the state of a phase change material (PRAM), such as a chalcogenide alloy, or a variation in the resistance of a magnetic tunnel junction (MTJ) thin film according to the magnetization state of a ferromagnetic substance (MRAM).
A resistive memory cell generally includes a first electrode, a second electrode, and a variable resistive material interposed therebetween, and the resistance level of the variable resistive material varies according to a voltage applied between the first and second electrodes. In particular, in some embodiments, a filament serving as a current path of a cell current may be formed in the variable resistive material. A state in which a portion of the filament is cut may be defined as a reset state, a high-resistance state, and/or reset data (1 data), and a state in which filament is connected may be defined as a set state, a low-resistance state, and/or set data (0 data). Other techniques of providing high and low resistance states also may be used.
A reset voltage having a sufficient voltage level to cut the filament or otherwise provide a high resistance state may be supplied to write reset data in the resistive memory cell, and a set voltage having a sufficient voltage level to connect the filament or otherwise provide a low resistance state may be supplied to write set data in the resistive memory cell. In addition, a voltage having a sufficiently low voltage level not to change the state of the filament or resistance may be supplied to read out the stored reset data or set data.